Human papillomaviruses occur worldwide, affecting humans and the animal kingdom. Of the genital types affecting humans there are high and low risk types. The high-risk types are linked to the development of low and high-grade dysplasia and cervical cancer. Oncogenic strains of HPV have been found in 99.7% of cervical cancers. They are also associated with vulval, anal and penile carcinoma. Low risk types are associated with genital wart and low-grade dysplasia. Worldwide it has been estimated that 325 million women have either subclinical HPV or HPV-related clinical lesions.
The uterine cervix is particularly vulnerable to the effects of HPV infection at the transformation zone, which is an area where the stratified squamous cells of the vagina change over to become the columnar cells lining the endocervix and uterus. Cervical dysplasia can be either squamous or glandular in origin. Squamous dysplasia is more common, but the frequency of glandular lesions is increasing. The area of cell changeover is termed the metaplastic area, and most HPV associated cervical lesions occur within this area.
The presence of persistent HPV infection is thought to be a prerequisite for the development and maintenance of second and third stage cervical intraepithelial neoplasia (CINIII), ie. severe or precancerous dysplasia.
Current treatment of severe uterine cervical dysplasia (squamous epithelial lesions or glandular) is by surgically removing the areas of the uterine cervix that may possibly be involved. Treatment initially requires cytology, colposcopy and biopsy, and then a surgical treatment such as laser excision, loop excision or cold coagulation of the uterine cervix.
Complications of surgical treatment of uterine cervical dysplasia include cervical stenosis, constriction and complete sealing of the os, pelvic endometriosis following hematometra, painful and prolonged menstruation, excessive eversion of columnar epithelium, infection, bleeding, pain, psychological morbidity, infertility, and an incompetent cervix. Disease may recur after treatment and even progress to invasive cancer. Some women are distressed by having Pap smear abnormalities even though they are not considered to be serious, and in order to alleviate their concerns, many women with low-grade lesions are unnecessarily treated. The other reason for unnecessary treatment of low grade lesions is the concern of the treating physician that the patient may fail to attend for further follow-up and consequently progress to high-grade disease.
No treatment for early HPV infection of the uterine cervix (i.e. where only the virus is detected and there are no clinically evident changes) is currently undertaken, and in most circumstances the diagnosis of early infection is discouraged, one of the reasons being lack of treatment. Current treatments are for the consequences of late stage changes in cells of the uterine cervix (CINI, CINII, CINIII), caused by human papillomavirus infection. Other chemical treatments of the uterine cervix are being explored, eg. imiquimod (a drug which acts by promoting the body's immune response to HPV) but as yet have not been reported as successful.
The anus is also particularly vulnerable to the effects of human papillomavirus infection, particularly at the transformation zone where the stratified squamous cells of the anal verge change over to the columnar epithelial cells of the rectum.
Current treatment for anal dysplasia is either surgical removal or, in many cases, observational if severe extensive infection is present. If the dysplasia is very severe and involves the whole circumference of the anal canal, surgical treatment is to remove the whole area and provide a colostomy. Because the operation is so radical, and the duration of time to progress from anal dysplasia to anal cancer is not known, an observational approach is usually undertaken and the individual treated when cancer arises. No treatment for early human papillomavirus infection (where only the virus is detected and there are no clinically evident changes) of the anal canal epithelium currently exists.
The skin of the vulva, penis and anal verge is commonly infected, and these are thought to be the sites from which infection spreads to genital orifices. No treatment is currently given for human papillomavirus infection of the skin when there are no clinical manifestations and dysplasia is absent. Laser ablation has been attempted previously but failed to eradicate the infection.
It is known that iodine in the form of povidone-iodine is effective in treating many viruses including bovine papillomavirus. The latter is reported in D. C. Sokal et al, “Inactivation of papillomavirus by low concentrations of povidone-iodine”, Sexually Transmitted Diseases Vol 22, No. 1 (January-February 1995) 22-24, which suggests that povidone-iodine or other agents might reduce the rate of sexual transmission of the human papillomavirus associated with cervical cancer.
Povidone-iodine solution has relatively low tissue toxicity and has been used in topical formulations for disinfection, wound antisepsis, the treatment of burns, and the treatment of non-specific vaginitis. Povidone-iodine is available in over-the-counter preparations as a douche, vaginal gel, and vaginal suppository for the symptomatic treatment of minor vaginal irritation and itching.
By way of example, U.S. Pat. No. 5,035,883 discloses the use of povidone-iodine complex by applying an aqueous or aqueous alcoholic solution of the complex in the treatment of non-oral and non-periodontal human disorders. There is specific mention of vaginal infection and papillomavirus infection.
A form of iodine has been applied topically to the uterine cervix in the Schiller's test. In this test, Lugol's iodine is applied to the uterine cervix and the observed colour change is used to either detect HPV infected tissue or demarcate areas for treatment. The glycogen in fully differentiated genital epithelium takes up the iodine, staining the tissue dark brown. The application of iodine is used to distinguish between metaplasia (iodine negative) and HPV associated lesions (partial uptake).
A number of prior references describe intra-uterine catheters with single inflatable balloons, typically for sealing the entrance to the uterine cavity. For example, in Canadian patent 1,313,803, the balloon, which is inflated with the actual fluid being introduced into the uterine cavity, seals an extended region in the vicinity of the internal os. The devices of European patent publication 0088714 and U.S. Pat. No. 5,372,584 are generally similar save that the sealing balloon sits clearly within the uterine cavity immediately inwardly of the internal os.
An object of the present invention is to endeavour to reduce the incidence of uterine cervical dysplasia (all stages) and cervical cancers, and to avoid the more radical treatments of uterine cervical dysplasia, by treatment of early HPV infection of the uterine cervix.
A further object is to similarly endeavour to reduce the incidence of anal dysplasia and anal cancers.